Hydraulic fracturing is the main process to improve the productive formation bottomhole zone permeability by making fractures and/or widening and deepening of the natural cracks therein. For this purpose a high pressure fracturing agent is pumped into the borehole crossing the underground formation. The formation deposits or rock is forced to cracking and fracturing. The proppant is pumped into the crack to prevent the fracture closing after the formation pressure is released, it provides improved fluid (i.e., oil, gas or water) production.
To conduct hydraulic fracturing activities hydraulic fracturing fluids with different rheology are used depending on the activity purposes and formation properties. In case of high-permeable formations high-viscosity fracturing fluids are injected into a fracture and characteristic velocity of such flows are low. Such flows are usually laminar, i.e., different flow strata are not mixed. However, during the hydraulic fracturing activities in low-permeable formations (for example, at shale gas fields) low-viscosity fracturing fluids with large injection rates are used. Such flows may lose stability which results in the fact that the flow becomes turbulent when all the flow characteristics get chaotic in all the scale lengths. In case of a turbulent flow the suspension in the fracture is constantly mixed. It usually results in significant changes in the particle distribution because the chaotic pulsations result in the uniform distribution of the proppant particles across the fracture. Large-scale vortexes prevent the particles from settling and maintain them suspended thus reducing the particles' settling rate.
In U.S. Pat. No. 6,776,235 a method of a formation hydraulic fracturing is proposed in which a proppant settling rate is adjusted by controlling the injection rate. However, this method does not provide monitoring of the flow mode of the fracturing fluid being injected and does not allow ensuring uniform proppant filling of the entire fracture assisting the formation of relatively dense proppant packages in the sporadically located fracture areas.
The method being suggested provides for a real time monitoring of a hydraulic fracturing fluid flow in a fracture and in a borehole with subsequent injection parameter adjustment depending on the specific purposes of the formation hydraulic fracturing activities aimed at increased hydrocarbons inflow.